This is what causes muscles to work which can require a breakdown, and also to build in the rest period, which occurs during the strengthening phase associated with muscular contraction. The Metabolic Research Center team consists of doctors, nutritionist, online consultants, nurses, and other medical professionals. So, we had our research team examine everything that is included in the Metabolic Research Center program, giving you the information necessary to make your own decision. Sure, they might be enough to give you a few pounds of weight loss when you are just starting out. Several mechanisms were suggested to explain fiber-induced ghrelin suppression, most importantly fermentation.
Side effects and drug interactions should also be considered. What you want from your fat burner is simple — effectiveness. The majority of supplements on the market claiming to drastically improve weight-loss have no clinical backing, but there are a few bright lights out there. The ECA stack, which stands for ephedra, caffeine and aspirin, is a clinically-proven fat burner. The ephedra part of the formula is no longer legal for use by companies offering fat burners.
The ingredients work synergistically with ephedra elongating the time caffeine is present in the body and the aspirin thinning the blood to get everything moving faster. The mild hot tea you drink every morning may offer more than you thought. When combined with caffeine, green tea can spark thermogenesis. EGCG is found in green tea. This spice can be used for more than seasoning food. There is some connection between chili powder and increased energy expenditure, which leads to fat loss.
Another ingredient in your kitchen also has some fat burning qualities. Clinical studies have proven protein can improve thermogenesis or fat burning.
Just because a fat burner is proven to work, does not mean it is safe for everyone. The earliest formal definition of fiber refers to the source of fiber: This definition was soon updated to include nondigestible polysaccharides that are not part of the plant cell wall [ 28 ], in order to account for storage carbohydrates such as guar gum. However, this definition remains limiting as fibers can also be obtained from animal, fungal, bacterial, and synthetic sources. Categorization based on source is also complicated by the inability of analytical methods to distinguish fiber origin [ 29 ].
Chemically, fiber can be described based on its chain length and type of linkages between each monomeric unit. This provides a very precise and unequivocal meaning; however, deciding on the appropriate chain length for fiber has been difficult. The physiological effects of fiber refer to its nondigestibility and metabolic effects. Nondigestibility in the small intestine is fundamental to fiber and was part of the first definition put forth by Trowell [ 27 ].
However, nondigestibility and a lack of absorption by the small intestine alone do not guarantee favourable physiological effects. Depending on physicochemical properties, fibers have a range of physiological consequences including viscosity in the upper gastrointestinal tract [ 31 , 32 ], fermentation in the colon [ 33 ], and prebiotic effects [ 34 , 35 ]. These effects in the gastrointestinal tract improve laxation and increase stool bulking and also have metabolic consequences including improvements in serum lipids and postprandial glycemia and promotion of satiety.
Analytical definitions are used for labelling and inspection purposes. The risk with these types of definitions is that they are not able to recognize new fiber compounds, which may have significant and beneficial health implications.
This type of definition is very practical from a regulatory point of view; however, it alone does not actually describe any characteristics of fiber and an analytical method should only be part of a formal regulatory definition. The most recent definitions for fiber generally address at least one of four characteristics: With the advances of food science, isolation, modification, and synthesis of many fibers are possible, which have resulted in some jurisdictions distinguishing between naturally occurring fibers from plant source and isolated or synthesized fibers.
Others have chosen not to adopt this division by either considering all nondigestible carbohydrates as fiber or only those carbohydrates that are intrinsic and intact in plants. Table 1 lists examples of such definitions based on this division. As seen in the previous section, fibers are often classified by their source plant, animal, isolated, synthetic, etc. Chemical classification can divide carbohydrates based on their chain length, or DP: However, some carbohydrates do not fit into this categorization.
For instance, inulin may have from 2 to fructose units and thus can be both oligo- and polysaccharide [ 35 ]. Fibers are most commonly characterized based on their solubility. Distinction between soluble and insoluble dietary fibers is based on the solubility characteristics of dietary fiber in hot aqueous buffer solutions [ 38 ].
Solubility of dietary fiber structure cannot be simply described as the solubility in water. Solubility of dietary fibers is rather defined as dissolved or liquefied in a buffer and enzyme solution modeled after, but not necessarily identical to, the aqueous enzyme solutions or slurries present in the human system [ 39 ].
Solubility can be used as a means to broadly characterize the physiological effects of fibers. In general, insoluble fibers increase fecal bulk and the excretion of bile acids and decrease intestinal transit time i.
Soluble fibers increase total transit time by delaying gastric emptying and also slow glucose absorption [ 40 ]. Although this characterization of fiber is used to generalize the effects of each fiber type, only soluble viscous fibers delay gastric emptying time and slow glucose absorption while nonviscous soluble fibers primarily act as a substrate for microbial fermentation in the colon [ 33 ]. The rate at which a carbohydrate is digested is determined by a number of factors, including the rate at which carbohydrate leaves the stomach and becomes available for absorption as well as diffusion of released sugars occurs from food bolus [ 41 ].
Thus, the rate at which carbohydrates leave the food matrix and the ability for amylase to act on the carbohydrate is an important determinant of glucose absorption rate and resulting blood glucose levels. Based on digestion, carbohydrates can be categorized as rapidly or slowly digested or even resistant.
Resistant carbohydrates include plant cell wall polysaccharides, gums, fructans, resistant maltodextrins, and resistant starches. These carbohydrates that resist digestion make their way to the large intestine, where they may be fermented by the gut microflora [ 33 ] or have prebiotic effects [ 34 ].
However, not all fiber is fermented. Short-chained fatty acids produced from fermentation are mainly sourced from resistant starches [ 42 , 43 ]. Prebiotic fibers alter the balance of the gut microflora towards what is considered to be a healthier one [ 34 ] and includes fructans and resistant starches [ 45 ]. For food labelling purposes, it is important that analytical methods complement the fiber definition in a given jurisdiction.
Fibers are typically measured by enzymatic-gravimetric methods, although there are also gravimetric, nonenzymatic-gravimetric, and enzymatic chemical methods. Fibers recovered with enzymatic-gravimetric methods include cellulose, hemicelluloses, pectins, some other nonstarch polysaccharides, lignin and some resistant starch. Soluble and insoluble fibers can also be measured separately by this method [ 46 ].
However, these methods do not capture inulin and polydextrose and partially measure resistant starch. To remedy this, separate procedures have been proposed to quantify these other compounds. Resistant starch, oligofructan, inulin, fructo-oligosaccharides, and polydextrose can also be measured independently by several methods [ 29 ]. However, these methods incompletely measure all fibers included in the Codex definition, and the use of some or all of these methods could result in underestimation of some fibers as well as overestimation of others due to double counting.
It is also particularly important for food labelling that fiber analysis be completed on foods as they would be eaten in order to provide more accurate fiber values that account for the effects of processing and cooking procedures [ 49 ]. The AOAC method Dietary fibers have been strongly implicated in the prevention and treatment of various characteristics of the metabolic syndrome.
The beneficial effect of fiber-rich foods and isolated fibers, both insoluble and soluble, on obesity, cardiovascular diseases, and type 2 diabetes has been shown in randomized studies [ 6 , 11 ]. Diets rich in fiber improve glycemic control in type 2 diabetes [ 54 ], reduce low-density lipoprotein LDL cholesterol in hypercholesterolemia [ 55 — 57 ], and contribute positively to long-term weight management [ 58 ].
In epidemiological studies, positive associations were noted between increased cereal consumption, a source of both insoluble and soluble fibers, and reduced risk of metabolic syndrome, cardiovascular diseases, and markers of systemic inflammation [ 59 — 61 ]. Diets rich in whole-grain foods have also been negatively associated with metabolic syndrome [ 6 , 8 , 11 ]. In comparison to insoluble fibers, soluble fibers are more potent in attenuating the presence of components of the metabolic syndrome in both animals and humans.
Serum leptin levels were normalized and insulin sensitivity index was improved. The diet supplemented with the soluble fermentable fiber Plantago Ovata husks also resulted in the greatest improvement in hyperinsulinemia and hyperleptinemia, and lowered the production and accumulation of lipids in the liver. This effect was associated with activation of the AMP-activated protein kinase AMPK system [ 63 ], known to increase fatty acid oxidation and decrease fatty acid synthesis [ 64 ].
Moreover, a high fiber meal, in which refined-wheat flour was replaced with whole-wheat flour High adiponectin levels are associated with improved glycemic control and insulin sensitivity, a more favorable lipid profile and reduced inflammation in diabetic females [ 68 ]. Glucans from barley, oats, or wheat are found in cell walls of the endosperm, while being concentrated in the aleurone layer of barley, oats, wheat, sorghum, and other cereals.
They are major structural components of the cell walls of yeast, fungi, and some bacteria [ 75 ]. These glucans are important for plant-microbe interactions, and act as signalling molecules during plant infection [ 76 ]. However, no sharp distinction exists between the insoluble and soluble fractions and the ratio is highly dependent on the extraction conditions of the soluble fiber [ 82 ].
This conformation allows for stronger interactions and associations between chains than between the chains and water molecules. Solubility increases as the degree of polymerization is lowered. One study completed in mice found that effects of chronic consumption of chitin-glucan from a fungal source improved metabolic abnormalities induced by a high fat diet [ 99 ]. In this particular study, chitin-glucan decreased high fat diet-induced body weight gain, fat mass development, fasting hyperglycemia, glucose intolerance, hepatic triglyceride accumulation, and hypercholesterolemia, irrespective of caloric intake.
These benefits include lowering postprandial glucose and insulin responses, decreasing cholesterol levels, and potentiating the feelings of satiety. Insulin resistance, whether or not accompanied with hyperglycemia, and type 2 diabetes are well-established components of metabolic syndrome [ ].
Beta glucan also contributes to glycemic control. Several factors were found to influence such an interaction, including dose, food form, and molecular weight. In subjects with noninsulin-dependent diabetes mellitus, consumption of three breakfasts with 4, 6, and 8.
Consumption of oat bran providing 7. The consumption of oat bran flour containing 9. This is perhaps because wheat pasta itself has a low glycemic response. One of the mechanisms includes the ability of soluble fibers to form viscous solutions. Delayed gastric emptying occurs with increased digesta viscosity [ — ], slowing subsequent digestion and absorption [ ]. High digesta viscosity decreases enzyme diffusion [ ] and stimulates the formation of the unstirred water layer [ ], decreasing glucose transport to enterocytes [ 31 ].
Reducing the viscosity of guar gum following acid hydrolysis resulted in concurrent loss of its clinical efficacy [ 31 ]. A relationship was noted between guar gum viscosity and its glycemic response. Similarly, the addition of 13 C-labelled glucose to a meal containing 8. Individuals with metabolic syndrome often present with atherogenic dyslipidemia, characterized by elevated concentrations of triacylglycerols and low levels of HDL cholesterol in blood [ 3 ].
This lipid profile presents an individual with a high risk for cardiovascular disease. Soluble fibers have the most reported beneficial effects on cholesterol metabolism. In a meta-analysis, soluble fibers pectin, psyllium, oat bran, and guar gum were all proven to be equally effective in reducing plasma total and LDL cholesterol levels [ 55 ]. Conversely, soluble fibers from barley, oats, psyllium, and pectin had no effect on HDL cholesterol levels [ 55 , ].
Variable effects of soluble fibers on triglyceridemia have been noted. In two meta-analyses, soluble fibers, including barley, oats, psyllium, and pectin, had no significant impacts on triglyceride concentrations [ ].
Other studies have described hypotriglyceridemic effects of soluble fibers in various populations. The soluble fiber in Plantago Ovata husk reduced triglyceridemia in human secondary cardiovascular disease risk trials, when consumed at Discrepancies in findings could be attributed to the variability in fiber structure, the degree of solubility and viscosity, different administered doses, the duration of administration, and baseline triglyceride levels of the subjects.
However, other studies found no hypocholesterolemic effect of incorporating oats into bread [ , — ]. The activation of these enzymes depends on the processing technique used in bread making. Altering bile acid excretion and the composition of bile acid pool is one of the mechanisms. Beta glucans can decrease the reabsorption of bile acids and increase their transport towards the large intestine [ ], promoting their increased microbial conversion to metabolites and their higher excretion, subsequently inducing increased hepatic synthesis of bile acids from circulating cholesterol [ ].
In addition, some soluble fibers decrease the absorption of dietary cholesterol by altering the composition of the bile acid pool. In fact, oat bran increased the portion of total bile acid pool that was deoxycholic acid [ ], a microbial byproduct of bile acid which decreases the absorption of exogenous cholesterol in humans [ ]. Fermentation changes the concentration of bile acids in the intestinal tract of rats [ ] as well as the production of short-chain fatty acids, which influence lipid metabolism.
For example, propionate is thought to suppress cholesterol synthesis, though results are still inconclusive [ — ] and acetate may contribute to the lowering of cholesterol circulating levels [ ]. It should be well noted that differences between soluble fibers in the relative production of acetate, propionate, butyrate, and total short-chain fatty acids do exist.
However, such differences may not be that important to generate varied degrees of hypocholesterolemic impacts among soluble fibers.
Two mechanisms include a possible delay in the absorption of triglycerides in the small intestine [ ], as well as a reduced rate of glucose absorption [ ].
Glucose-induced hypertriglyceridemia, via the process of de novo lipogenesis, is well established in the literature [ ]. Furthermore, direct inhibition of lipogenesis by soluble fibers is also suggested as an explanatory mechanism.
The hypotriglyceridemic effect of oligofructose was reported to result from the inhibition of hepatic lipogenesis via the modulation of fatty acid synthase activity [ , ]. Hypertension is another core component of the metabolic syndrome, and is an established risk factor for heart diseases, stroke, and renal diseases [ ]. In one meta-analysis, increased dietary fiber consumption provided a safe and acceptable means to reduce blood pressure in patients with hypertension [ ].
In another randomized parallel-group study on hypertensive and hyperinsulinemic men and women, the oat cereal group standardized to 5. Various mechanisms underlying the antihypertensive effects of soluble dietary fibers have been hypothesized.
Insulin resistance is a major underlying mechanism contributing to the development of hypertension [ ] and soluble fibers may affect blood pressure by modulating insulin metabolism [ ]. Reductions in plasma cholesterol, observed following the ingestion of soluble fibers, are also associated with improvements in endothelium-mediated vasodilation [ , ]. Preliminary findings in animals support a direct relationship between changes in circulating cholesterol levels and blood pressure [ ].
Finally, soluble fiber-induced weight loss, which will be discussed in the coming section, has also been suggested as a potential mechanism. Increased body weight is a strong risk factor for hypertension [ ]. In conclusion, additional studies are still needed in order to fully elucidate the mechanisms underlying the protective effects of soluble fibers against hypertension. Central obesity is a well-established component of the metabolic syndrome [ 3 ]. One potential countermeasure to the current obesity epidemic is to identify and recommend foods that spontaneously reduce energy intake by inducing satiation and increasing satiety.
Dietary fiber has documented effects on satiety, food intake, and body weight although the outcomes have not been consistent [ ]. A number of randomized controlled trials have shown weight reduction with diets rich in dietary fiber or dietary fiber supplements [ — ], while others have not [ ]. More specifically, the soluble dietary fiber glucomannan, which has a strong water-holding capacity, resulted in a significantly greater reduction of weight, when consumed at a dose of 1.
Despite the clear association between soluble fibers and weight loss, their effects on subjective measures of satiety are not conclusive.
For example, the addition of 2. The soluble resistant dextrins promoted, in a dose-dependent manner, increased satiety when added to desserts and to carbohydrate-based meals [ — ].
Moreover, a nutrition bar containing guar gum 5. Subjects described to be significantly less hungry before lunch after consuming barley—but not wheat—and rice-containing foods [ ]. Barley-based foods enhanced as well satiety when compared to a high-glycemic index food or a food with no dietary fiber [ — ]. Similarly, a preload of 5. This was also associated with a significant reduction of energy intake at the subsequent lunch [ ].
In contrast, a meal replacement bar containing 1. Dose is one of the major determinants. Solid foods are known to increase satiety and decrease hunger more effectively than liquid ones [ ].
Moreover, another concern to be addressed in future studies is the type of control to use. No dietary fiber that may function as a control for satiety studies has been actually identified.
It should be noted that the body weight was not the primary concern of these studies as they focused on changes in blood sugar or blood lipids. The satiating properties of soluble dietary fibers have been explained by various mechanisms, all of which are related to several stages in the process of appetite regulation such as taste, gastric emptying, absorption, and fermentation [ ]. Firstly, the viscosity of soluble fibers plays an important role in their ability to induce satiety [ , , ].
A higher viscosity meal delays gastric emptying [ , , ] and slows the digestion and absorption of nutrients, more precisely glucose, due to reduced enzymatic activity and mucosal absorption [ 31 , ], leading to early satiety sensations.
The overall gastric emptying rate of healthy volunteers, as assessed by the paracetamol absorption test, was slower after the high viscosity oat bran-enriched beverage as compared to the low viscosity drink [ ]. Secondly, the lower palatability of fiber-rich meals may affect food intake in a negative manner [ — ]. A strong inverse relationship is described between palatability and satiation [ ]. A significant inverse relationship is reported between satiety and glucose and insulin responses to carbohydrate-rich breakfast cereals [ , ] and to beverages with different glycemic effects [ ].
However, other studies did not report any association of glucose and insulin postprandial levels with satiety [ , ]. They suggested that the release of putative satiety peptides is a more crucial component of mechanisms initiating and maintaining satiety.
Such statement leads to the fourth suggested mechanism that delineates the role of short-chain fatty acids in appetite control. Short-chain fatty acids regulate the release of various gut hormones, which play an important role in satiety signaling. The role of short-chain fatty acids in appetite regulation and the potential underlying mechanisms will be elucidated in the following sections. The fermentability of soluble fibers by colonic microbiota is greater than that of insoluble fibers. Pectin, resistant starches, gums, and polyfructans such as inulin are the most highly fermented substrates.
On the other hand, acetate passes more freely into the peripheral circulation [ ]. Several functions are attributed to short-chain fatty acids, being recently proposed as key energy homeostasis signaling molecules [ ].
Accumulating evidence has attributed the satiating effects of fermentable carbohydrates to short-chain fatty acids, their major fermentation products [ ]. Short-chain fatty acids regulate appetite through several mechanisms.